Subscriber&#39;s calling device in electroacoustic transmission apparatus



O. TSCHUMI SUBSCRIBERS CALLING DEVICE IN ELECTRO-ACOUSTIC TRANSMISSION APPARATUS Filed May 12, 1944 AT U3 Patented Aug. 21, 1945 SUBSCRIBERS CALLING DEvIoE' IN ELEC- TROACOUSTIO TRANSMISSION APPARA- TUS Otto T schumi, Soleure, Switzerland, assignor to Autophon Aktiengesellschaft, Soleure, Switzerland, a joint-stock company of Switzerland Application May 12, 1944, Serial No. 535,294 In Switzerland November 6, 1942 6 Claims. (01.179481) I In app ratus of this kind calling takes place either by direct speaking or bya special audio frequency-calling signal. However, in both cases,

t e person calling after the call and the change of the speakingdirection, can hear things going on in the room of the person calling if there are not signalling bells independent of the a'ctual' transmi-sison apparatus.

The ubscribers calling device according to the invention remedies these. inconveniences. It is characterised by the fact that in the subscribers station means are provided-allowing the speaking signals'to be locked at will in one or both speaking directions.

The accompanying drawing illustrates, by way of example, one embodiment of the invention: 7

Fi 1 shows in a diagrammatic way the subscribers device and v Fig. 2 a scheme of the repeater connected to the exchange of the subscribers device,

Referring now toEig. 1, EW designates an electrosacoustic transformer which may be Iused both. as transmitter and as receiver, In the working moment shown in the drawing it is connected with the input trans-former ET of the amplifier V through the switch to, while the output transformer AT is in connection with the repeater LU through the Switch u2 and the :contact SHL. On the side of the line this repeater is earthed in the middle (at M1). The free ends are connected with the outlet terminals as and b2, the contact 81-12 with the terminals 1 and 2, bridged over by the condenser 0, being interconnested in the one branch (b2). j

Referring now to Fig. 2, the terminals a1, and 121 of the repeater U connected to the exchange 'of the subscribers device are connected with a2 and 77 A differential relay X, which comprises the single windings X1 and X2 and which is bridged-over by a condenser and arranged to be short-circuited by the contact n of the relay is connected to the middle of the repeater winds ing on the subscribers side in such a way that between the single win ings X1 and X2 lies the middle-point M2 which is connected to the negative element of a battery. By the relay contact 12 the call winding is connected with an audiofrequency generator transmitting the calling signal, while the winding on the side of the line leads to the line terminals a and b and can be disconnected from the line by the difierentia'l relay contact.

If it be desired to call up the subscriber. the relay is caused to actuate by non-illustrated means and its contacts 1'1 and T2 are closed. Contact r1 connectsthe terminals 3 and 4 of the winding on the side of the subscriber, whereby the differential'relay X is neutralised, while contact 72 connects the call winding of the repeater U with the non-illustrated audio-frequency genorator. Owing to the neutralisation of the relay X, its contact a: remains in the represented rest position; with the efiect that the person calling can, for the sake of control, also hear the calling signal.

When calling up, the position of the contacts SH1 and SHz is that illustrated, while the switches in and uz are brought by non-illustrated means'into the opposition position (position II) and, likewise in a non-represented manner, an alternating current is connected or superposed to the negative terminal. This alternating current which, on the one side is earthed and, on the'other side, connected to the negative terminal, is transmitted through the windings X1, X2, the left-hand winding of the repeater U with condenser, the terminals a1, a2 and b1, D2 to the repeater LU which is earthed at M1. From the repeater LU the calling signal is transmitted through in to the input transformer ET of the amplifier V and through the output transformer AT to the electro-acoustic transformer EW serving as receiver. Therefore, the calling signal is transmitted both to the transformer EW and to the person calling.

At the-moment when the person calling breaks the calling signal, the relay R is without current, contacts 1'1 and 12 drop, the diiierential relay X is no longer short-circuited and the call winding of therepeater is disconnected from the audiorrequency generator. Since X is no longer short cuited and 3:1 and :02 are no longer connected in parallel, and since, furthermore, SHz is still open and-keeps the branch M2b1-b2-M1 without current, contrary to the branch M2a1azM1, sci thus carrying current and m not, X comes into action and its contact a: separates the person calling from the repeater. The device thereby locks all incoming calling signals while the open position of SH1 guarantees that no speaking signals can be transmitted.

To answer the call, the contacts SI-I1 and SHz are closed and the switches a1 and 1L2 brought into the position shown in the drawing. In this way, the electro-acoustic transformer EW, now working as a transmitter, is connected with az 172 through m, the amplifier V, 1L2-SH1--LU. Since contact SHz is closed, the two branches connected in parallel and each closed by .a Winding of the differential relay X (1'1 and x2) are symmetrical. Relay X remains neutralised and contact an guarantees the transmission of the calling signals transmitted by the transformer EW to the line ab. When the switches U1 and 1L2 are brought into the other position, the conditions for a communication with the subscriber are fulfilled.

If, on the other hand, the terminals I and 2 are short-circuited and the contacts SH1 and SH2 open, or if only contact S111 is open while contact SHz is closed, the device locks all outgoing signals owing to the open contact SI-Ir, while both the call and the incoming signals are received in EW.

The contacts SH1 and SHz being closed, communications in both directions are possible according to the manner in which the amplifier is connected-in between transformer and repeater by the switches in and uz.

Therefore, with the device according to the invention it is possible, by merely operating the contacts SH1 and 5H2 and by a corresponding connection of the switches in and m to obtain a series of speaking, locking and calling possibilities:

Calling: The signal is received in EW Without the subscriber having the possibility of transmitting. The person calling can, for control, hear the signal in, U2 in position II, SE5, SE2 open.

After the calling, the device locks every signal both the incoming and outgoing ones. To answer the call the switches m, 11.2 must be in position I and the contacts SH1, SHz closed.

For revertive communication the switches in, M2 must be brought into position II.

When in and w in position II, Sl-hopen, SHz closed, or, if SHi and SHz are under the influence of the same operating lever: SE1 and 8112 open, terminals I and 2 in conductive connection: locking of all outgoing signals, open for all incoming signals.

According to the needs required and in adaptation to the actual local conditions all desirable kinds of transmission can be obtained by simple switching-over.

What I claim is:

1. In an electro-acoustic transmission apparatus, a subscribers calling device including a subscribers station, means in said subscribers station. destined to allow the speaking signals to be locked at will in one or both speaking directions, these means comprising two switches capable of effecting the change in the direction of communication, and two contacts to be controlled by the subscriber.

2. In an electro-acoustic transmission apparatus, a subscribers calling device including a subscribers station, means in said subscribers station, destined to allow the speaking signals to be locked at will in one'or both speaking direc tions, these means comprising two switches capable of effecting the change in the speaking direction, two contacts to be controlled by the subscriber, and two circuits connected in parallel, in relation with said contacts in order to be made symmetrical or asymmetrical by the influence of One of said contacts.

3. In an electro-acoustic transmission apparatus, a subscribers calling device including a subscribers station, means in" said subscribers station, destined to allow the speaking signals to be locked at will in one or both speaking directions, these means comprising, two switches capable of efiecting the change in the speaking direction, two contacts to be controlled by the subscriber, two circuits connected in parallel, in relation with said contacts in order to be made symmetrical or asymmetrical by the influence of one of said contacts, lines, switching means destined to switch in and off said lines, said switching means being controllable by the asymmetry of said two circuits connected in parallel.

4. In an electro-acoustic transmission apparatus, a subscribers calling device including, a

subscribers station, means in said subscribers station, destined to allow the speaking signals to be locked at will in one or both speaking directions, these means comprising two switches capable of effecting the change in the speaking direction, two contacts to be controlled by the subscriber, two circuits connected in parallel, in relation with said contacts in order to be made symmetrical or asymmetrical by the influence of one of said contacts, lines, a differential relay destined to switch in and off said lines, said differential relay being controllable by th asymmetry of said two circuits connected in parallel.

5. In an electro-acoustic transmission apparatus, a subscribers calling device including, a subscribers station, means in said subscribers station, destined to allow the speaking signals to be locked at will in one or both speaking directions, these means comprising two switches capable of effecting the change in th speaking'direction, two contacts to be controlled by'the subscriber, two circuits connected in parallel, in relation with said contacts in order to be made symmetrical or asymmetrical by the influence of one of said contacts, and a further contact in relation with the call, a part of said parallel circuits bein short-circuited by said further contact. 6. In 'an electro-acoustic transmission apparatus, a subscribers calling device including a subscribersstation, means in said subscribers station, destined to allow the speaking signals to be locked at will in one or both speaking direc-- tions, these means comprising two switches capable of effecting the change in th speaking direction, two contacts to be controlled by the subscriber, two circuits connected in parallel, in relation with said contacts in order to be made symmetrical or asymmetrical bythe influence of one of said contacts, lines, switching means controllable by the asymmetry of said two circuits connected in parallel, and a further contact in relation with the call, a part of said parallel circuits being short circuited by said further contact in such a way that said switching means does, in spite of the existing asymmetry of said two parallel circuits, not come into action.

' O'I'IO TSCHUMI. 

